Those dammed beavers: shifts in benthic invertebrate food webs and assemblages in their ponds

Beavers act as ecosystem engineers by modifying landscapes and changing lotic ecosystems to lentic ones, thereby creating wetlands. Sedimentation rates decrease in beaver ponds, allowing these ponds to become potential sources of nitrogen, phosphorus, and carbon. By damming the stream, the water floods the surrounding area, asphyxiates the vegetation, and increases organic matter inputs into the pond. Despite the resurgence in beaver activity and research surrounding it, the broad-scale ecological impacts that beavers have on ecosystem processes, like food webs and community structure, are still largely unknown. Specifically, despite the increase in nutrients and basal resources, there is limited investigation on how beaver ponds can impact bottom-up controls in food webs. To address the effects beaver ponds have on ecological processes, I conducted a comparative experiment on the beaver ponds and the adjacent streams in Happy Jack Forest/Pole Mountain, WY, USA. In July and August 2022, benthic macroinvertebrates and basal resources were collected from beaver ponds and streams using handheld nets and Surber samplers for food web and community structure analysis. I found that macroinvertebrate food webs have shifted in the beaver ponds compared to the streams. Algae was the dominant food resource in ponds, while plants were dominant in streams. Furthermore, the community structure from stream to pond ecosystems had changed, with abundance higher in ponds but diversity higher in streams. Length and mass of chironomid midge flies and limnephilid caddisflies were also higher in ponds compared to streams. The outcomes of this study give insight into indirect effects on stream ecosystem processes caused by beavers.